1. Field of the Invention
The present invention relates to an elastic wave device including a laminated film that includes a piezoelectric thin film and is laminated on a support substrate.
2. Description of the Related Art
In an elastic wave device disclosed in International Publication No. WO2012/086639, a laminated film is disposed on a support substrate and a piezoelectric thin film is laminated on the laminated film. The laminated film includes a high-acoustic-velocity film and a low-acoustic-velocity film. The low-acoustic-velocity film is a film through which a bulk wave propagates at an acoustic velocity lower than an acoustic velocity at which a bulk wave propagates through the piezoelectric thin film. The high-acoustic-velocity film is a film through which a bulk wave propagates at an acoustic velocity higher than an acoustic velocity at which an elastic wave propagates through the piezoelectric thin film. The low-acoustic-velocity film is laminated on the high-acoustic-velocity film. Interdigital transducer (IDT) electrodes are disposed on the piezoelectric thin film.
In the elastic wave device disclosed in International Publication No. WO2012/086639, the piezoelectric thin film is made of a piezoelectric single crystal such as LiTaO3. Accordingly, the piezoelectric thin film may crack or chip when a multilayer body including the piezoelectric thin film and the laminated film is cut to obtain individual elastic wave devices in a dicing process.
In an elastic wave device including a support layer and a cover for providing a hollow space on the IDT electrodes, the sealability of the hollow space may not be sufficiently increased. Accordingly, sufficient reliability of the elastic wave device may not be ensured.